1. Field of the Invention
The present invention generally relates to systems and apparatus for determining a relative position of at least a portion of an implant within a living being, and more particularly, to systems and apparatus for determining at least one positional variable of the implant of choice.
2. Background Art
Implants, such as prosthetic implants, are often subject to forces over their implant life times that can cause at least a portion of the implant to move relative to the desired implant position. Often, the undesired movement of the implant can cause undue wear on the implant, potential failure of the implant, and limitations on the mobility of the patient. This undesired implant movement ultimately can cause the patient to undergo a revision or replacement implant surgery, which, in addition to the normal surgical risks, may not necessarily allow for the degree of mobility that the original implant afforded due to scar tissue formation and other surgical limitations that could be inherent to the particular implantation site.
The system and apparatus of embodiments described herein overcome at least the above-described disadvantages by providing an ability to accurately and non-invasively monitor the relative position of an implant positioned within the living being. As one will appreciate, it is desirable to gather information relating to the relative position of the implant in order to monitor the structural viability of the implant; to characterize the mechanical behavior of implant materials and structures under loading conditions; and to detect early sign of catastrophic failure events. Further, it is desirable to monitor the precise relative position of the implant within the living being non-invasively.
Exemplary biomedical applications of the relative position analysis described herein, without limitation, include its use in acute monitoring applications, such as, for example and without limitation, total disk replacement procedures and total knee replacement procedures and chronic monitoring applications.
For example, a total disk replacement procedure is typically recommended when the native disk is not able to perform its function as a cushion between two vertebrae. The total disk replacement procedure replaces the native disk and with a disk implant that is configured to restore appropriate spacing between adjoining vertebrae. Referring to FIG. 1, typically, a conventional artificial disk implant comprises end portions 6 that are configured to contact the bone and, in some case, provide a temporary or permanent anchoring of the artificial disk implant onto one or both vertebrae 1, 2 that under or overlie the native disk. Conventionally, the anchoring of the disk implant is achieved via mechanical fasteners, such as screws 11, biocompatible cements, and the like. Conventionally, the disk implant also has pliant section 8 that is interposed between the end portions and that is configured to emulate the function of the original disk. The pliant section should, at least in theory, be able to absorb shocks and allow motion to occur between the two adjoining vertebrae while maintaining desired alignment. The degrees of freedom as well as the amplitude of the tolerated motion are dictated by design, choice of material, etc. It is beneficial to the surgeon performing the disk replacement surgery to know the precise distance measurements between various portions of the implant prosthesis and/or between portions of the implant prosthesis and the adjoining tissues, such as, for example, bone tissue, both during the replacement surgery and in the days, months, and years after the implantation of the implant prosthesis.